Investigators are preparing to quiz the coroner this August, as part of a probe which could take up to three years

The coroner responsible for overseeing the first inquests into the Hillsborough disaster is to be questioned by police to establish why he ordered checks on the blood alcohol levels of those who died.

In a letter to vicitims' families, the Independent Police Complaints Commission (IPCC) said it was preparing to quiz Dr Stefan Popper this August, as part of a larger probe which could take up to three years.

Dr Popper will also be asked to reveal the contact he had with police officers at the time of the 1989 disaster, according to reports by the Liverpool Echo.

Former Merseyside chief constable Norman Bettison, who resigned as West Yorkshire chief constable in October over the Hillsborough cover-up, could also be asked to give evidence to investigators as early as May this year.

The probe, which is still in its preliminary stages but officially begins next month, is currently seeking information from several high-profile figures who were in power at the time, including former Prime Minister Margaret Thatcher.

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Terrifying: The Hillsborough disaster

The IPCC, a non-departmental public body which oversees complaints made against police in England and Wales, is examining whether the original police report on the tragedy provided an "accurate and complete picture".

Its director of quality and standards, Mike Benbow, a former police officer of 30 years, has been put in charge of the investigation.

New inquests into the 96 deaths will be held this year after the Lord Chief Justice Lord Judge sensationally quashed the original “accidental death” verdict which was controversially imposed in 1991.